AD 95-13-08

This amendment supersedes an existing airworthiness directive (AD), applicable to Pratt & Whitney Canada (PWC) PT6A-67D turboprop engines, that currently requires inspections of the compressor turbine (CT) disk and blades for cracking and other irregularities using visual inspections and fluorescent penetrant inspections (FPI). That AD also requires amending the Beech Model 1900D Airplane Flight Manual (AFM) and installing a placard that alerts the pilot of a requirement to restrict continuous engine operation above 94.0% and below 97.1% N1 (Gas Generator RPM). In addition, that AD requires the installation of parts having an improved design including a CT stator assembly, a CT shroud housing, CT turbine blades, feather seals, and a small exit duct assembly. This amendment continues the requirements of the current AD and adds the requirements to remove the placard from the cockpit and to remove the amendment to the AFM after installation of the improved engine components.This amendment is prompted by reports from operators and the manufacturer stating that the engine RPM operating restriction is not required after installation of the improved engine components, and that this engine operating restriction can impact aircraft handling. The actions specified by this AD are intended to prevent aircraft handling problems due to imposition of the engine RPM restriction.

Final rule; request for comments.

95-13-08 Pratt & Whitney Canada: Amendment 39-9288. Docket 95-ANE-33. Supersedes AD 94-10-02, Amendment 39-8909.
Applicability: Pratt & Whitney Canada (PWC) Model PT6A-67D turboprop engines with serial numbers prior to PC-E114100, installed on but not limited to Beech Model 1900D airplanes. NOTE: This airworthiness directive (AD) applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (o) to request approval from the Federal Aviation Administration (FAA). This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any engine from the applicability of this AD.
Compliance: Required as indicated, unless accomplished previously.
To prevent aircraft handling problems due to imposition of the engine RPM restriction, accomplish the following:
(a) For those operators that have previously complied with AD 94-10-02, this AD requires compliance with only paragraph (n).
(b) Prior to further flight, amend the Beech Model 1900D Aircraft Flight Manual (AFM), Part Number (P/N) 129-590000-3, by inserting the following requirements between pages 2-4 and 2-5:
"ENGINE OPERATING LIMITATIONS
Gas Generator RPM (N1) - Continuous operation of the gas generator between 94.0% and 97.1% is prohibited.

NOTES

1. This limitation does not prohibit the use of N1's between 94.0% and 97.1% when the pilot in command determines that the power setting is required for the safe operation of the airplane. If such occurrences exceed 5 minutes, the engine(s) must be inspected in accordance with Pratt & Whitney Canada Service Bulletin No. 14128, Revision 3, dated April 19, 1993.
2. This limitation does not prohibit the use of static Take-Off Power and Maximum Continuous Power between 94.0% and 97.1% N1 to meet the required Take-Off performance. If such occurrences exceed 5 minutes, the engine(s) must be inspected in accordance with Pratt & Whitney Canada Service Bulletin No. 14128, Revision 3, dated April 19, 1993.
3. Operation at 94.0% and below, and at 97.1% and above are permitted. Continuous operation at 94.1% through 97.0% is prohibited.
4. "Continuous Operation" means time periods exceeding 5 minutes.
5. High Speed Cruise Power Tables found in the Pilot's Operating Manual may produce N1's in the prohibited range. Flights should be planned using Intermediate or Long RangePower settings. 6. The goal of the operator should be to keep the total time of operation in the prohibited range to the absolute minimum, since the effects of operating between N1's of 94.0% and 97.1% are cumulative. PLACARDS
Located in front of the pilot on the aft edge of the glareshield between the Master Caution annunciator and the fire extinguisher control switch:

CONTINUOUS OPERATION BETWEEN
94.0% AND 97.1% N1 IS PROHIBITED
SEE AFM"

(c) Compliance with the requirements of paragraph (b) of this AD may also be accomplished by inserting a copy of this AD into the Beech Model 1900D AFM.
(d) Prior to further flight, install the placard as specified in paragraph (b) of this AD.
(e) For engines that have not been inspected prior to the effective date of this AD in accordance with PWC SB No. 14128, Revision 1, dated November 13, 1992, or debladed and inspected in accordance with PWC SB No. 14128, Revision 2, dated December 22, 1992, or PWC SB No. 14128, Revision 3, dated April 19, 1993, accomplish the following:
(1) For engines with Serial Numbers PC-E114001 to PC-E114044, within 25 hours time in service (TIS) after the effective date of AD 94-10-02, June 15, 1994, deblade the CT disk, inspect the entire disk surface area and fir tree area of the CT blades for cracking and the trailing edge of the blade airfoil section for irregularities, and replace, if necessary, with serviceable parts, in accordance with the Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated April 19, 1993.
(2) For engines with Serial Numbers PC-E114045 to PC-E114099, within 50 hours TIS after the effective date of AD 94-10-02, June 15, 1994, deblade the CT disk, inspect the entire disk surface area and fir tree area of the CT blades for cracking, and replace, if necessary, with serviceable parts, in accordance with the Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated April 19, 1993.
(f) For engines that have been inspected in accordance with PWC SB No. 14128, Revision 1, dated November 13, 1992, prior to the effective date of this AD, deblade the CT disk, inspect the entire disk surface area and fir tree area of the CT blades for cracking, and replace, if necessary, with serviceable parts, in accordance with the Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated April 19, 1993, as follows:
(1) For blade sets with greater than 600 hours TIS since new on the effective date of AD 94-10-02, June 15, 1994, deblade, inspect, and replace, if necessary, within the next 50 hours TIS after the effective date of AD 94-10-02, June 15, 1994.
(2) For blade sets with greater than or equal to 250 hours TIS, and less than or equal to 600 hours TIS, since new, on the effective date of AD 94-10-02, June 15, 1994, deblade, inspect, and replace, if necessary, within the next 100 hours TIS after the effective date of AD 94-10-02, June 15, 1994.
(3) For blade sets with less than 250 hours TIS since new onthe effective date of AD 94-10-02, June 15, 1994, deblade, inspect, and replace, if necessary, within the next 250 hours TIS after the effective date of AD 94-10-02, June 15, 1994.
(g) For uninstalled CT disk and blade assemblies that have not been inspected in accordance with the Accomplishment Instructions of PWC SB No. 14128, Revision 2, dated December 22, 1992, or PWC SB No. 14128, Revision 3, dated April 19, 1993, in the preceding 250 hours TIS from the effective date of AD 94-10-02, June 15, 1994, deblade the CT disk, inspect the entire disk surface area and fir tree area of CT blades for cracking, and replace, if necessary, with serviceable parts, in accordance with the Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated April 19, 1993, prior to installation.
(h) For engines with CT disk and blade assemblies that have been debladed and inspected in accordance with the Accomplishment Instructions of PWC SB No. 14128, Revision 2, dated December 22, 1992, or PWC SB No. 14128, Revision 3, dated April 19, 1993, prior to the effective date of AD 94-10-02, June 15, 1994, within 250 hours TIS since the last deblading and inspection, deblade the CT disk, inspect the entire disk surface area and fir tree area of CT blades for cracking, and replace, if necessary, with serviceable parts, in accordance with the Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated April 19, 1993.
(i) For CT disk and blade assemblies that have been debladed and inspected in accordance with paragraphs (e), (f), (g), and (h) of this AD, deblade the CT disk, reinspect the entire disk surface area and fir tree area of CT blades for cracking, and replace, if necessary, with serviceable parts, in accordance with the Accomplishment Instructions of PWC SB No. 14128, Revision 3, dated April 19, 1993, at intervals not to exceed 250 hours TIS since the last deblading and inspection performed in accordance with the Accomplishment Instructions of PWC SB No. 14128,Revision 3, dated April 19, 1993.
(j) Install a CT stator assembly, a CT shroud housing, and a small exit duct assembly in accordance with PWC SB No. 14132, Revision 1, dated May 12, 1993, at the next shop visit after the effective date of this AD, or within 30 days after the effective date of this AD, whichever occurs first.
(k) Install CT blades and feather seals in accordance with PWC SB No. 14142, Revision 1, dated May 12, 1993, at the next shop visit after the effective date of this AD, or 30 days after the effective date of this AD, whichever occurs first.
(l) For the purpose of this AD, a shop visit is defined as when major engine flanges are separated.
(m) Installation of improved hardware in accordance with paragraphs (j) and (k) of this AD constitutes terminating action for the inspections required by paragraphs (e) through (i) of this AD.
(n) For aircraft equipped with engines that have complied with paragraphs (j) and (k) of this AD, or AD 94-10-02, accomplish the following:
(1) Remove the amendment to the Beech Model 1900D AFM, P/N 129-590000-3, described in paragraphs (b) or (c) of this AD.
(2) Remove the placard described in paragraph (d) of this AD.
(o) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Engine Certification Office. The request should be forwarded through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office.
NOTE: Information concerning the existence of approved alternative methods of compliance with
this AD, if any, may be obtained from the Engine Certification Office.
(p) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the aircraft to a location where the requirements of this AD can be accomplished.
(q) The inspections and modifications shall be done in accordance with the following SB's:

Document No.
Pages
Revision
Date
PWC SB No. 14128
1-5
3
April 19, 1993
Total pages: 5.

PWC SB No. 14132
1-6
1
May 12, 1993
Total pages: 6

PWC SB No. 14142
1-7
1
May 12, 1993
Total pages: 7.

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Pratt & Whitney Canada, 1000 Marie-Victorin, Longueil, Quebec, Canada J4G 1A1. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(r) This amendment becomes effective on July 12, 1995.

On May 16, 1994, the Federal Aviation Administration (FAA) issued airworthiness directive (AD) 94-10-02, Amendment 39-8909 (59 FR 25295, May 16, 1994), applicable to Pratt & Whitney Canada (PWC) PT6A-67D turboprop engines, to require deblading the compressor turbine (CT) disk; and inspecting the entire disk surface area and fir tree areas of the CT blades for cracking and the trailing edge of the blade airfoil section for irregularities, using visual inspections and fluorescent penetrant inspections (FPI). These inspections are required until installation of parts having an improved design: turbine blades, feather seals, and a small exit duct assembly. That AD also requires amending the Beech Model 1900D Airplane Flight Manual (AFM) by inserting requirements that describe restricting continuous engine operation above 94.0% and below 97.1% N1 (Gas Generator RPM); and installing a placard that alerts the pilot of this restriction. That action was prompted by reports of CT blade failures due to high cycle fatigue (HCF) fractures in the fir tree area of the blade while exposed to normal engine vibrations and by the manufacturer developing new design improvements that will reduce the susceptibility of the CT blades to HCF damage. That condition, if not corrected, could result in aircraft handling problems due to imposition of the engine RPM restriction.
Since the issuance of that AD, operators of Beech 1900D aircraft and the manufacturer have stated that the engine RPM operating restriction is not required after installation of the improved engine components, and that the engine operating restriction can impact aircraft handling. The placard and AFM amendment currently restrict continuous engine operation above 94.0% and below 97.1% N1, where continuous operation is defined as time periods exceeding 5 minutes. In some situations, this restriction could require the pilot to adjust the engine power level during critical flight segments, such as takeoff, thus increasing pilot workload. Therefore, this superseding AD repeats the compliance requirements of the current AD, and adds the requirement to remove the placard from the cockpit and remove the amendment to the AFM after installation of the improved engine components.
This engine model is manufactured in Canada and is type certificated for operation in the United States under the provisions of Section 21.29 of the Federal Aviation Regulations and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, Transport Canada has kept the FAA informed of the situation described above. The FAA has examined the findings of Transport Canada, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.
PWC has issued Service Bulletin (SB) No. 14128, Revision 3, dated April 19, 1993, that specifies procedures forCT blade inspections; SB No. 14132, Revision 1, dated May 12, 1993, that specifies procedures for CT stator vane replacement; and SB 14142, Revision 1, dated May 12, 1993, that specifies procedures for CT blade replacement. Transport Canada classified these service bulletins as mandatory and issued AD CF-92-25-R1, dated June 1, 1993, in order to assure the airworthiness of these PWC PT6A-67D engines in Canada.
Since an unsafe condition has been identified that is likely to exist or develop on other engines of this same type design, this AD supersedes AD 94-10-02 to continue the requirements of the current AD and add the requirements to remove the placard from the cockpit and to remove the amendment to the AFM after installation of the improved engine components. The actions are required to be accomplished in accordance with the SB's described previously.
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity forprior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would beneeded.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 95-ANE-33." The postcard will be date stamped and returned to the commenter.
The regulations adopted herein will not have substantial direct effects on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows: PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. 39.13 - [AMENDED]
2. Section 39.13 is amended by removing Amendment 39-8909, (59 FR 25295, May 16, 1994), and by adding a new airworthiness directive, Amendment 39-9288, to read as follows: